1. Field of the Invention
The invention relates in general to a wireless communication technique, and more particularly, to a technique for detecting spectrum inversion in a wireless communication signal.
2. Description of the Related Art
With advancements in communication techniques, digital television broadcasting continues to mature. Apart from being transmitted via cables, digital television signals can also be transmitted in a form of wireless signals via a base station or a satellite. The Digital Video Broadcasting-Satellite (DVB-S) and the Digital Video Broadcasting-Satellite-Second Generation (DVB-S2) are prevalent standards in digital television broadcasting.
In the DVB-S2 specifications, an input signal received at a baseband demodulator at a digital television signal receiving end is a signal that is processed by π/2-shifted binary phase shift keying (BPSK), and is composed of an in-phase component and a quadrature component. In practice, a tuner and a mixer at a DVB-S2 receiving end may misinterpret the in-phase component and the quadrature component as each other—such a situation is referred to as spectrum inversion. If such a situation is not timely detected by the baseband demodulator, an activation failure of a television system may occur even after having had already performed numerous signal processing procedures. To correct the activation failure, the in-phase component and the quadrature component need to be exchanged, followed by repetition of the same signal processing procedures. It is obvious, therefore, that the issue of spectrum inversion may severely delay a power-on time of the television system.